It's so tough isn't it. My DS was the same age and was just the same.
Interestingly, his behaviour outside of home worsened with DD's arrival too.
We're 18 months on (and a lot of guilt, tears, shouting, guilt, etc etc) and I'm beginning to realise that while things are much harder work, DS's life is enriched by having his little sister around. I interpret his worsened behaviour as a negative/jealous reaction to DD but when it's just me and him now - I desperately missed that time - he keeps asking where she is and wants to get back to her. They have some truly lovely moments together. DD doesn't have many words yet but she signs a lot and often strokes his hair or points while trying to say his name and does her sign for 'love' (like a hug against her chest).
I can't pretend we're finding it easy yet and his behaviour is still much worse when around DD... BUT... some of his kindest, most thoughtful moments have been around her too. I'm also gradually beginning to understand what drives the behaviour and which approaches work best for him.
Re bedtime - we tried to keep things as consistent as possible. I would make sure DD was fed and tucked up in bed (even when she was tiny and downstairs in her moses basket and we knew she wouldn't be there for long), then leave DH in charge of soothing! I would take DS up for his story and chat which gave him some time alone with me and some sense of continuity. It was quite hard to do, but because I knew DD was fed and with DH I would just shut the door and ignore any crying for those 10 minutes and eventually DS did too. He did go through a stage of coming to the top of the stairs but either me or DH would just go and give him a big cuddle and put him straight back to bed. There are many, many things I'd like to go back and do differently, but that's the one thing I think we got right! Is your DH around in the evening?
naps - Would going for a drive help? DS only napped in the car by that stage anyway, but for him it was the move from cot to bed which had messed up naptime so nothing new there!
That's quite long! I know just how you feel though. It will get easier, I promise. Try to look after yourself too, I forgot that bit and got quite ill which didn't help.